Printing ink composition of solvent recovery/reuse type, diluent solvent, and method of reusing recovered solvent

ABSTRACT

A method of recovering and recycling solvents, comprising, during printing or coating of solvent-recoverable and recyclable printing ink composition comprising solvents, a step of recovering the solvents vaporized in a solvent recovery apparatus, a step of separating the solvents obtained into one or more single solvents and/or one or more azeotropic compositions of two or more solvents by multi-stage distillation, and a step of recycling them as a printing ink raw material and/or dilution solvent raw material.

TECHNICAL FIELD

The present invention relates to a recyclable solvent and an inkcomposition containing the same. The present invention also relates to amethod of recovering and recycling the vaporized solvents generatedduring printing. The present invention further relates to a solventcomposition and an ink composition containing the recovered solvent.

BACKGROUND ART

Recently, there are increasing concerns about air pollution such asdestruction of ozone layer in stratosphere, in lower atmosphere damageto agricultural products and forest resources by acid rain, and badeffects on the body by photochemical oxidants. Laws and regulations forprevention of air pollution is becoming strict year by year. Inparticular in the field of gravure printing, where organic solvents havebeen released in greater amounts, there is increased attention torecovery and recycling of solvents as a means to overcome these problems(Non-Patent Documents 1 to 3).

Actually in the fields of lamination adhesive and gravure printing,where ethyl acetate or toluene is used as a single solvent, solvents arealready recovered and recycled. However, in gravure printing for otherapplications (such as laminate printing, cover printing, paper printingand aluminum printing), a variety of inks are used according toapplications and thus, the number of solvents increases inevitablyconsidering the solubility of the resins and drying speed (Non-PatentDocuments 1 to 3).

When inks for various applications are used in a single printing machineor at a single factory or when solvents recovered at various places arecollected, conventional printing inks and dilution solvents gave themixture unstable in composition, because the mixture contained variouscomponents. For reuse, the recovered solvent should be fractioned intosingle solvents by using a large-scale distillation column. Thelarge-scale distillation column demands large initial and running costs.It also demanded a great amount of distillation energy, leading toconsumption of a large amount of oil resources, and discharged carbondioxide in a great amount. Thus, there has been a problem that the reusedid not lead to any cost reduction by recycling or any improvement inenvironmental friendliness.

Patent Document 1: Japanese Patent Application Laid-Open No. 07-247456

Non-Patent Document 1: Hideki Yasuda, J. Japanese Printing Society, Vol.43, No. 6, 404-410 (2006).

Non-Patent Document 2: Masashi Senmoto, J. Japanese Printing SocietyVol. 44, No. 1, 8-14 (2007).

Non-Patent Document 3: Japan Environmental management Association forIndustry, Ed., Ministry of Economy, Trade and Industry contract surveyreport in 2005, “Studies on Measurements against Environmental HazardousSubstances (measures to prevent volatile organic compound (VOC)emission)”, March, 2006.

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

There has been a need for a method of recovering volatile solventsgenerated during printing and recycling the solvents easily. There wasalso a need for easy recycling solvents and printing inks containing thesame. Further, there was a need for recyclable solvents higher inprinting efficiency and printing inks containing the same.

Means for Solving the Problems

An aspect of the present invention relates to a recyclable printing inkcomposition (herein, referred to as solvent-recoverable and recyclableprinting ink composition), comprising two or more solvents selected fromhydrocarbon solvents, ketone solvents, ester solvents, alcoholicsolvents and glycol ether solvents.

The solvents are preferably selected from methylcyclohexane,methylethylketone, n-propyl acetate, isopropyl alcohol and propyleneglycol monomethylether. The composition may comprise three or more ofthe solvents above.

In addition, 95% or more of the total amount of the solvents maycomprise two organic solvent components. The two organic solventcomponents may be n-propyl acetate and isopropylalcohol. In such a case,the component ratio (by weight) of n-propyl acetate to isopropyl alcoholis preferably in the range of 60:40 to 90:10. The two solvent componentsmay be ethyl acetate and isopropyl alcohol. In such a case, thecomponent ratio (by weight) of ethyl acetate to isopropyl alcohol ispreferably in the range of 20:80 to 50:50.

Another aspect of the present invention relates to a solvent-recoverableand recyclable printing ink composition, comprising a polyurethane resinformed with a polymer polyol, an organic isocyanate compound and a chainextender as the main binder and the solvents above.

Yet another aspect of the present invention relates to asolvent-recoverable and recyclable dilution solvent composition,characterized by being identical with the organic solvent in thesolvent-recoverable and recyclable printing ink composition above.

Yet another aspect of the present invention relates to a coated article,comprising the solvent-recoverable and recyclable printing inkcomposition above.

Yet another aspect of the present invention relates to alaminatedarticle, prepared by coating the solvent-recoverable and recyclableprinting ink composition above on a film, and laminating orcompression-bonding the film thus obtained.

Yet another aspect of the present invention relates to a method ofrecovering and recycling solvents, comprising, during printing orcoating of solvent-recoverable and recyclable printing ink compositioncomprising solvents, a step of recovering solvents vaporized in asolvent recovery apparatus, a step of separating the solvents obtainedinto one or more single solvents and/or one or more azeotropiccompositions of two or more solvents by multi-stage distillation, a stepof analyzing the composition of the obtained azeotropic composition ifnecessary, a step of adjusting the composition of the separated solventsif necessary, and a step of recycling them as a printing ink rawmaterial and/or dilution solvent raw material. The solvents may compriseat least three kinds of solvents selected from hydrocarbon solvents,ketone solvents, ester solvents, alcoholic solvents and glycol ethersolvents. In addition, the solvents may be at least three kinds ofsolvents selected from methylcyclohexane, methylethylketone, n-propylacetate, isopropyl alcohol and propylene glycol monomethylether. Themethod may further comprise, after the step of recovering the solventsand before the step of separation, a step of removing water by at leastone method selected from membrane separation, adsorption, specificdensity difference separation and distillation.

Yet another aspect of the present invention relates to a method ofrecovering and recycling solvents, comprising, during printing orcoating with a solvent-recoverable and recyclable printing inkcomprising two organic solvents in an amount of 95% or more, a step ofrecovering solvents vaporized in a solvent recovery apparatus, a step ofanalyzing the composition of the solvents recovered as needed, a step ofadjusting the composition of the solvents, and a step of recycling it asa printing ink raw material and/or a dilution solvent raw material. Theanalysis step is preferably carried out by at least one method selectedfrom gas chromatography, liquid chromatography, infrared absorptionspectrometry, refractive index measurement, density ratio measurement,conductivity measurement, nuclear magnetic resonance absorption methodand odor test method. The solvents may comprise an ester solvent and analcoholic solvent. The solvents may be n-propyl acetate and isopropylalcohol. In such a case, the component ratio (by weight) of n-propylacetate to isopropyl alcohol is preferably in the range of 60:40 to90:10. The solvents may comprise ethyl acetate and isopropyl alcohol. Insuch a case, the component ratio (by weight) of ethyl acetate toisopropyl alcohol is preferably in the range of 20:80 to 50:50.

Yet another aspect of the present invention relates to a printing inkcomposition, comprising the solvents separated into one or more singlesolvents and/or one or more azeotropic compositions of two or moresolvents by the method above.

Yet another aspect of the present invention relates to a printing inkdilution solvent composition, comprising the solvents separated into oneor more single solvents and/or one or more azeotropic compositions oftwo or more solvents by the method above.

The disclosures in the present description relate to the subjects of thepatent applications: Japanese Patent Application No. 2006-162122 (filedon Jun. 12, 2006), Japanese Patent Application No. 2006-197960 (filed onJul. 20, 2006), Japanese Patent Application No. 2006-226157 (filed onAug. 23, 2006), Japanese Patent Application No. 2007-110868 (filed onApr. 19, 2007) and Japanese Patent Application No. 2007-153652 (filed onJun. 11, 2007), the entire disclosures of which are incorporated hereinby reference.

EFFECT OF THE INVENTION

According to an aspect of the present invention, it is possible torecover the solvents vaporized during printing and recycle the solventseasily. According to another aspect of the present invention it is alsopossible to provide an easily recyclable solvent composition and aprinting ink composition comprising the same. According to anotheraspect of the present invention, it is possible to provide a recyclablesolvent composition higher in printing efficiency and a printing inkcontaining the same.

According to yet another aspect of the present invention, it is easilypossible to recycle solvents even if the recovered solvents generated inmore than one printing machines, facilities or companies are mixedtogether.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a chart showing examples of the solvent recovery recyclingaccording to the present invention.

BEST MODE OF CARRYING OUT THE INVENTION

The solvent recovery recycling method according to the present inventionof recovering and recycling the solvents generated during printing orcoating by using the solvent-recoverable and recyclable printing inkcomposition containing solvents comprises a step of recovering solventsvaporized in a solvent recovery apparatus, a step of separating thesolvents obtained into one or more single solvents and/or one or moreazeotropic compositions of two or more solvents by multi-stagedistillation, and as needed a step of analyzing the solvents of theazeotropic composition, as needed a step of adjusting the composition ofthe separated solvents, and a step of recycling it as a printing ink rawmaterial or a dilution solvent raw material.

When the solvent-recoverable and recyclable printing ink compositionaccording to the present invention containing a two-component organicsolvent in an amount of 95% or more is used, the solvent recoveryrecycling method includes a step of recovering solvents vaporized in asolvent recovery apparatus, a step of analyzing the composition of thesolvents obtained, and a step of recycling the solvents as a printingink raw material or a dilution solvent raw material by adjusting it withan added solvent component.

The solvent-recoverable and recyclable printing ink composition maycontain solvents, resins and colorants.

The solvent for use in the solvent-recoverable and recyclable printingink according to the present invention may be any solvent, such as wateror an organic solvent, commonly used in gravure printing, flexographicprinting, letterpress printing, roll coating, spray coating or dipcoating. Examples of the organic solvents include various solvents, andamong them, favorable are hydrocarbon solvents, ketone solvents, estersolvents, alcoholic solvents, and glycol ether solvents. Most resins aresoluble in a hydrocarbon solvent, a ketone solvent, an ester solvent oran alcoholic solvent. Glycol ether solvents are advantageous foradjusting drying speed. Therefore, inks in most applications can bedesigned in combination of these solvents. Three or more solvents amongthem may be used as mixed, or two solvents may be used as mixed. Whentwo solvents are mixed, combination of an ester solvent and an alcoholicsolvent is preferable. When two solvents are used in combination, it ispossible to prepare an ink more favorable in printability thanconventional inks, allowing easy recycling of the solvents aftercompositional adjustment.

Examples of the hydrocarbon solvents include, but are not limited to,aliphatic hydrocarbon solvents such as n-hexane, n-heptane and n-octane;alicyclic hydrocarbon solvents such as cyclohexane, methylcyclohexane,ethylcyclohexane, cycloheptane and cyclooctane; and aromatic hydrocarbonsolvents such as toluene. Examples of the ketone solvents include, butare not limited to, acetone, methylethylketone, methylisobutylketone,dimethyl carbonate and the like. Examples of the ester solvents include,but are not limited to, methyl acetate, ethyl acetate, n-propyl acetate,butyl acetate, propylene glycol monoethylether acetate and the like.Examples of the alcoholic solvents include, but are not limited to,methanol, ethanol, n-propanol, isopropyl alcohol, butanol and the like.Examples of the glycol ether solvents include, but are not limited to,propylene glycol monomethylether, propylene glycol monoethylether andthe like.

Considering the solubility, drying efficiency and printing workingenvironment, the hydrocarbon solvents are preferably aliphatic solvents,and among them, methylcyclohexane is preferable. The ketone solvents arepreferably methylethylketone, because it has a drying speed favorablefor gravure printing and relatively low level of odor. The estersolvents are preferably n-propyl acetate because it has favorable dryingspeed and favorable solubility, or ethyl acetate because it is usedwidely as a solvent in production of various resins and has highdissolving potential for many resin system. The alcoholic solvents arepreferably isopropyl alcohol, because it has a favorable drying speedand a relatively low level of odor, and the ink prepared with anisocyanate-based hardening agent is superior in storage stability. Theglycol ether solvents are preferably propylene glycol monomethylether,because it has a drying speed favorable as a slow-vaporization solventand relatively low level of odor.

The favorable blending rate of respective solvents varies according tovarious conditions. For example, (1) the blending rate of a hydrocarbonsolvent is preferably 0 to 90 wt % in all solvents, for assurance ofsolubility for example when a rubber or petroleum resin is used; (2)that of a ketone solvent, preferably 0 to 90 wt %, for assurance ofsolubility for example when a vinyl chloride-vinyl acetate copolymerresin is used; (3) that of an ester solvent, preferably 0 to 90 wt %,for assurance of solubility for example when a polyurethane resin isused, (4) that of an alcoholic solvent preferably 0 to 50 wt %, becausea rate of more than 50% may cause brushing by absorption of a greatamount of water during printing and lead to deterioration in wettabilityto the base material; (5) that of an glycol ether solvent, preferably 0to 20 wt %, because a rate of more than 20% leads to increase in theresidual amount in print and adverse effects on the downstreamprocessing and quality.

In particular, when 95% or more of the total amount of the solvents arepreferably two components: n-propyl acetate and isopropyl alcohol, andused together with a polyurethane resin the ratio thereof is preferably60:40 to 90:10, considering the solubility of the polyurethane resin,and more preferably 70:30 to 85:15 for prevention of fluctuation insolvent composition during continued use.

When the solvent is a two component system of ethyl acetate andisopropyl alcohol and used with a polyurethane resin, the ratio ispreferably 20:80 to 50:50 for favorable drying speed and more preferably30:70 to 50:50 for favorable solubility of the polyurethane resin.

These solvents may be selected appropriately, according to thesolubility of the resin system contained in the printing ink compositionused and the adjustment of drying rate for favorable printingefficiency. A smaller number of solvent species is favorable forrecovery and recycling of the solvents with smaller energy.Alternatively, use of many solvent species allows design of printing inkcompositions favorably used in a variety of applications. A solventcontent of 20 to 90 wt % with respect to the total weight of the ink ispreferable, and a content of 40 to 80 wt % is more preferable, from theviewpoint of the viscosity favorable for the storage stability and theprintability of the resulting ink.

In addition to the solvents described above, small amounts of someunintended solvent components, for example derived from additives orfrom the surrounding atmosphere may contaminate the ink compositionduring printing. However, these solvents may be contained, if the kindsand/or the amounts thereof are in the level that does not affect thesteps of printing, recovery and others.

Examples of the colorants used in the solvent-recoverable and recyclableprinting ink composition according to the present invention includeinorganic pigments, organic pigments and dyes.

Examples of white inorganic pigments include, but are not limited to,titanium oxide, zinc oxide, zinc sulfide, barium sulfate, calciumcarbonate, chromium oxide, silica and the like. Among them, use oftitanium oxide is favorable, from the points of coloring efficiency,masking efficiency, chemical resistance, weather fastness.

Examples of non-white inorganic pigment include, but are not limited to,pigments such as carbon black, aluminum, and mica. Aluminum is powder orpaste, but aluminum paste is preferable from the points of handlingefficiency and safety; and use of leafing or non-leafing aluminum pasteis determined properly according to the desired brightness and density.

Examples of the organic pigments include, but are not limited to,azo-based, phthalocyanine-based, anthraquinone-based, perylene-based,perynone-based, quinacridone-based, thioindigo-based, dioxazine-based,isoindolinone-based, quinophtharone-based, azomethine azo-based,diketo-pyrrolopyrrole-based, isoindoline-based and other pigments.Copper phthalocyanine is preferably used in blue ink, and C.I. PigmentNo Yellow 83 is preferably used in transparent yellow ink, from thepoints of cost and lightfastness.

The colorants are preferably contained in an amount sufficient forassuring the density and coloring efficiency of the printing inkcomposition, i.e., at a rate of 1 to 50 wt %, with respect to the totalweight of the printing ink. These colorants may be used alone or incombination of two or more.

The resin alone may be used for stable dispersion of the pigment inorganic solvents, but a dispersant may be used in combination, for morestable dispersion of the pigment. The dispersant for use may be ananionic, nonionic, cationic, ampholytic, or other surfactant. Thedispersant is preferably contained in an amount of 0.05 wt % or more,with respect to the total weight of the ink for improvement in storagestability and in an amount of 5 wt % or less for improvement inlamination compatibility. The content is more preferably in the range of0.1 to 2 wt %.

These pigments may be used alone or in combination of two or more, foradjustment of color tone and density. Also, dyes may be used alone or incombination, but use of a pigment is preferable from the viewpoint oflightfastness.

The resin for use in the solvent-recoverable and recyclable printing inkcomposition according to the present invention may be selected properlyaccording to the application and the base material used. Examples of theresins include polyurethane resins, polyurethane/urea resins, vinylchloride-vinyl acetate copolymer resins, chlorinated polypropyleneresins, ethylene-vinyl acetate copolymer resins, vinyl acetate resins,polyamide resins, nitrocellulose resins, acrylic resins, polyesterresins, alkyd resins, polyvinyl chloride resins, rosins, rosin-modifiedmaleic acid resins, terpene resins, phenol-modified terpene resins,ketone resins, cyclic rubbers, chlorinated rubbers, butyral, petroleumresins, and the like. These resins may be used alone or in combinationof two or more. The resin is preferably contained in an amount of 5 to25 wt % with respect to the total weight of the ink.

Requirements in film physical properties of the resin vary according toapplication of the printing ink, and thus, the kind of the resincontained in ink varies. For example, major applications of gravureprinting ink include printing on laminate film, cover film, paper, andaluminum foil. The ink for laminate film preferably contains apolyurethane/urea resin, a polyurethane resin, a chlorinatedpolypropylene resin, or a vinyl chloride-vinyl acetate copolymer resin.The ink for cover film preferably contains a polyamide resin. The inkfor paper preferably contains a nitrocellulose resin or an acrylicresin. The ink for aluminum foil preferably contains a nitrocelluloseresin, a chlorinated rubber resin or a vinyl resin.

Among the resins above, polyurethane resins are soluble when a mixtureof ester solvents and alcoholic solvents is used. Chlorinatedpolypropylene resins are soluble when a suitable amount of hydrocarbonsolvents is used; vinyl chloride-vinyl acetate copolymer resins aresoluble when a suitable amount of ketone solvents is used; polyamideresins are soluble when a suitable amount of alcoholic solvents is used;nitrocellulose resins are soluble when a suitable amount of estersolvents is used; acrylic resins are soluble when a suitable amount ofhydrocarbon or ester solvents is used; and chlorinated rubber resins aresoluble when a suitable amount of hydrocarbon solvents is used.

Alternatively, in the major application of printing ink, i.e., inprinting of laminate film, a polyurethane resin is often used as themain binder, for reduction in the amount of the solvents remaining inprint and also from the point of compatibility with extruding laminateprocessing. The polyurethane resin for use is, for example, apolyurethane resin used in common ink, paint or recording agent.

Such a polyurethane resin can be produced by using various known polyolscommonly used. The polyols may be used alone or in combination of two ormore.

The polyol is preferably converted into a urethane-modified polyol inreaction with a polyisocyanate and a chain extender. Theurethane-modified polyol can be produced by a prepolymer method ofproducing a terminal isocyanate group-containing prepolymer in reactionof a polyol and a polyisocyanate, as needed in the presence of a solventinert to the isocyanate group and additionally a urethane-convertingcatalyst, at a temperature of 10 to 150° C. and then obtaining apolyurethane polyol resin in reaction of the prepolymer with a chainextender. Alternatively, it can be produced by a known method, such asone-shot method, of obtaining a polyurethane polyol resin in a singlereaction of an organic polyol compound and a polyisocyanate compoundwith a chain extender.

Examples of the polyols include:

polyether polyols (1) of polymers or copolymers such as of methyleneoxide, ethylene oxide and tetrahydrofuran;

saturated or unsaturated low-molecular-weight polyols (2) such asethylene glycol, 1,2-propanediol, 1,3-propanediol, 2-methyl-1,3propanediol, 2-ethyl-2butyl-1,3 propanediol, 1,3-butanediol,1,4-butanediol, neopentylglycol, pentanediol, 3-methyl-1,5-pentanediol,hexanediol, octanediol, 1,4-butynediol, 1,4-butylenediol, diethyleneglycol, triethylene glycol, polypropylene glycol, dipropylene glycol,glycerin, trimethylolpropane, trimethylolethane, 1,2,6-hexanetriol,1,2,4-butanetriol, sorbitol, and pentaerythritol;

polyester polyols (3) obtained by dehydration condensation orpolymerization of the low-molecular weight polyol (2) with a polyvalentcarboxylic acid such as adipic acid, phthalic acid, isophthalic acid,terephthalic acid, maleic acid, fumaric acid, succinic acid, oxalicacid, malonic acid, glutaric acid, pimelic acid, suberic acid, azelaicacid, sebacic acid, trimellitic acid, or pyromellitic acid, or theanhydride thereof;

polyester polyols (4) obtained by ring-opening polymerization of acyclic ester compound (e.g., lactone) such as polycaprolactone,polyvalerolactone or poly(β-methyl-γ-valerolactone);

polycarbonate polyols (5) obtained in reaction of the low-molecularweight polyol (2), for example, with dimethyl carbonate, diphenylcarbonate, ethylene carbonate, phosgene or the like;

polybutadiene glycols (6);

glycols (7) obtained by addition of ethylene oxide or propyleneoxide tobisphenol A;

acrylpolyols (8) obtained by copolymerization of a compound having oneor more hydroxyethyl, hydroxypropyl acrylate or hydroxybutyl acrylate,or the corresponding methacrylate derivative, for example with acrylicacid or methacrylic acid, or the ester thereof;

polyether polyols (9) obtained by polymerization of an oxirane compoundsuch as ethylene oxide, propyleneoxide, butyleneoxide, ortetrahydrofuran by using a low-molecular weight polyol such as water,ethylene glycol, propylene glycol, trimethylolpropane, or glycerol asinitiator; and the like. In particular, polypropylene glycol ispreferable.

Examples of the polyisocyanates for use in the urethane-modified polyolinclude various known aromatic diisocyanates, aliphatic diisocyanates,alicyclic diisocyanates and others commonly used in production ofpolyurethane resins. Specific examples thereof include 1,5-naphthylenediisocyanate, 4,4′-diphenylmethane diisocyanate (MDI),4,4′-diphenyldimethylmethane diisocyanate, 4,4′-dibenzyl isocyanate,dialkyldiphenylmethane diisocyanate, tetraalkyldiphenylmethanediisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate,tolylene diisocyanate, butane-1,4-diisocyanate, hexamethylenediisocyanate, isopropylene diisocyanate, methylene diisocyanate,2,2,4-trimethylhexamethylene diisocyanate, lysine diisocyanate,cyclohexane-1,4-diisocyanate, xylylene diisocyanate, isophoronediisocyanate, dimethyl diisocyanate,dicyclohexylmethane-4,4′-diisocyanate,1,3-bis(isocyanatomethyl)cyclohexane, methylcyclohexane diisocyanate,norbornane diisocyanate, m-tetramethylxylylene diisocyanate,4,4-diphenylmethane diisocyanate, tolylene diisocyanate,bis-chloromethyl-diphenylmethane diisocyanate, 2,6-diisocyanatobenzylchloride, dimer diisocyanates (dimer acids having isocyanate groups inplace of carboxylic groups), and the like. These diisocyanate compoundsmay be used alone or as a mixture of two or more.

Examples of the chain extenders for use in production of theurethane-modified polyol include ethylenediamine, propylenediamine,hexamethylenediamine, diethylenetriamine, triethylenetetramine,isophoronediamine, and dicyclohexylmethane-4,4′-diamine, as well asamines containing hydroxyl groups in the molecule such as2-hydroxyethylethylenediamine, 2-hydroxyethylpropyldiamine,2-hydroxyethylpropylenediamine, di-2-hydroxyethylethylenediamine,di-2-hydroxyethylenediamine, di-2-hydroxyethylpropylenediamine,2-hydroxypropylethylenediamine, di-2-hydroxypropylethylenediamine, anddi-2-hydroxypropylethylenediamine. These chain extenders may be usedalone or as a mixture of two or more.

In addition, a monovalent active hydrogen compound can be used favorablyas a terminal blocking agent for termination of the reaction. Examplesof the compounds include dialkylamines such as di-n-butylamine andalcohols such as ethanol and isopropyl alcohol. In particular ifcarboxyl groups are desirably introduced into the polyurethane resin, anamino acid such as glycine or L-alanine may be used as the reactionterminator. These terminal blocking agents may be used alone or as amixture of two or more.

In production of a prepolymer, the amounts of the polyol and thepolyisocyanate are preferably adjusted at an equivalence ratio NCO/OH ofpolyisocyanate (F) isocyanate group to organic polyol compound hydroxylgroup in the range of 1.1 to 3.0. When the ratio is less than 1.1, it isoften difficult to obtain a sufficient alkali-resistant polymer, while aratio of more than 3.0 leads to deterioration in solubility of theobtained prepolymer.

Use of a solvent in reaction is preferable for control of the reaction.The solvent for use is preferably a solvent dissolving the polyurethaneadhesive composition, and favorable examples thereof include ketonessuch as acetone, methylethylketone, methylisobutylketone, andcyclohexanone; ethers such as dioxane and tetrahydrofuran; aromatichydrocarbons such as toluene and xylene; esters such as ethyl acetateand butyl acetate; and halogenated hydrocarbons such as chlorobenzeneand perchlene. These solvents may be used alone or as a mixture of twoor more.

A catalyst may be used additionally in the urethanation reaction.Examples of the catalysts favorably used include tertiary amine-basedcatalysts such as triethylamine and dimethylaniline; and metalliccatalyst such as tin and zinc. These catalysts are used normal in anamount in the range of 0.001 to 1 mol % with respect to the polyolcompound.

Reaction of the prepolymer obtained above having isocyanate groups atthe terminals with a chain extender such as diol, diamine, or triol at10 to 80° C. gives a high-molecular-weight polyurethane resin havingactive hydrogen groups at the terminals.

The terminal blocking agent, when added, may be used together with achain extender for chain-extending reaction, or alternatively, aterminal blocking agent may be added for termination of the reaction,after the chain-extending reaction proceeds to some extent with a chainextender. On the other hand, the molecular weight can be adjustedwithout use of a terminal blocking agent, but, in such a case, a methodof adding the prepolymer to a solution containing a chain extender ispreferable from the point of reaction control.

The terminal blocking agent is used for control of the molecular weight.Increase in amount leads to decrease in molecular weight of theresulting polyurethane resin. The equivalence ratio of the amino andhydroxyl groups in chain extender to the amino and hydroxyl groups interminal blocking agent is preferably in the range of 0.5 to 5.0,although it varies according to the reactivity of the chain extender andthe terminal blocking agent to the prepolymer. A ratio of more than 5.0may result in deterioration in dry lamination efficiency by increase inmolecular weight, while a ratio of less than 0.5 in lowering inmolecular weight and in deterioration in initial adhesive strength.

The reaction is favorably carried out, while the equivalence ratio ofthe total of the amino and hydroxyl groups in chain extender andterminal blocking agent to the isocyanate groups in the prepolymer iskept in the range of 1.1 to 3.0, preferably 1.5 to 2.0. When the ratiois large and the amount of the chain extender or the terminal blockingagent used is large, the reagent may remain unreacted, often leavingunpleasant odor.

The solvent-recoverable and recyclable printing ink compositionaccording to the present invention may contain additionally, as needed,various other additives such as extender pigment, leveling agent,antifoam, crosslinking agent, hardening agent, wax, silane-couplingagent, antirust agent, antiseptic agent, plasticizer, infraredabsorbent, ultraviolet absorbent, lightfastness improver, fragrance, andflame retardant.

The solvent-recoverable and recyclable printing ink compositionaccording to the present invention can be produced by using a commonlyused dispersing machine, such as dissolver, roller mill, ball mill,pebble mill, attriter, or sand mill. If air bubbles, unpredicted bulkyparticles, or the like are present in the solvent-recoverable andrecyclable printing ink composition, they are preferably removed, forexample, by filtration for prevention of deterioration in printingquality. Any known filter may be used for the filtration.

The viscosity of the solvent-recoverable and recyclable printing inkcomposition according to the present invention is preferably 10 mPa·S ormore for prevention of sedimentation of the pigment, and preferably 1000mPa·S or less from the viewpoints of processability during production ofprinting ink and during printing and also printing compatibilities suchas print staining resistance and leveling efficiency. The viscosity ismore preferably 10 to 500 mPa·S. The viscosity in the present inventionis a value obtained by using a rotating viscometer (BM viscometer,measured at 20° C.). The viscosity of the solvent-recoverable andrecyclable printing ink composition can be adjusted properly byselecting the kinds and amounts of the raw materials used such as resin,colorant, solvent, and others. The viscosity of the solvent-recoverableand recyclable printing ink composition can also be adjusted bymodifying the particle diameter and the particle diameter distributionof the pigment used in the composition.

Examples of the methods of printing or coating the solvent-recoverableand recyclable printing ink composition according to the presentinvention include printing methods such as gravure printing,flexographic printing and letterpress printing and coating methods suchas roll coating, spray coating and dip coating. The solvent-recoverableand recyclable printing ink composition is printed on a base material byone of the printing methods above, and fixed by vaporization of thesolvents in an oven.

The coated article according to the present invention can be prepared bycoating the solvent-recoverable and recyclable printing ink compositionaccording to the present invention on a base material by the printingmethod above and fixing it by drying in an oven. Examples of the basematerials include film-shaped and sheet-shaped base materials of variousresins including polyolefins such as polyethylene and polypropylene,polyesters such as polyethylene terephthalate, polycarbonate andpolylactic acid, polystyrene resins such as polystyrene, AS resins andABS resins, polyvinyl chloride, polyvinylidene chloride, cellophane,paper, aluminum; and the composite materials thereof. The base materialmay be previously surface-finished. Examples of the surface finishinginclude vapor deposition of metal oxide, coating with polyvinylalcohol,and corona treatment.

The laminated article according to the present invention can be preparedby coating an anchor coat on the printing or coating surface of theprint and additionally a laminate layer thereon. Examples of theanchor-coating agents include imine-based, isocyanate-based,polybutadiene-based and titanium-based coating agents. The laminatelayer may be formed by a known lamination step. The known laminationsteps include a common extrusion lamination method of laminating amolten polyethylene resin, a dry lamination method of coating anadhesive agent for example based on polyether urethane or polyesterurethane on a printing surface and laminating a plastic film thereon,and a direct lamination method of applying a molten polypropylenedirectly on the printing surface. The laminate layer may be, forexample, an aluminum foil, a metal vapor deposition film, and apolyethylene film.

The vaporized solvents are recovered in a solvent recovery apparatus.The solvent recovery apparatus is preferably installed in the printingmachine, because transportation of the vaporized solvents areundesirable, but may be installed separately from the printing machine.The solvents can be recovered in various patterns. For example, as shownin pattern A of FIG. 1, volatile organic solvents (VOCs) generated indifferent printing machines (printing machines (1) to (3)) in a printingcompany (printing company A) may be recovered in one solvent recoveryapparatus. Alternatively as shown in pattern B, volatile organicsolvents (VOCs) generated in printing machines (printing machines (1) to(3)) in different printing companies (printing companies A to C) may berecovered in different solvent recovery apparatuses. Yet alternativelyas shown in pattern C, volatile organic solvents (VOCs) generated fromthe same printing machine (printing machine (1)) in the same company(printing company A) on different days may be recovered in a solventrecovery apparatus.

The vaporized solvents are recovered by separating the solvent vaporfrom the air. Specific examples of the methods favorably used include,but are not limited to, condensation method, compression method,absorption method and adsorption method. The method used is selectedproperly, by taking into consideration of the composition, physicalproperties, chemical properties, concentrations, and generation amounts(treatment amounts) of solvent vapors as well as the impuritiescontained therein, desired recovery rate, and properties of therecovered solvents. In particular, gas adsorption method by using anabsorbent, which is favorable from the point of recovery rate and cost,is used generally.

Examples of the absorbents include, but are not limited to, activatedcarbon, porous silicas such as silica gel, zeolite, various clays,alumina, iron oxide (iron hydroxide gel), magnesium perchlorate, andion-exchange resins. Among them, activated carbon, a porous silica suchas silica gel, or zeolite, which has large specific surface area, isfavorably selected. The shape of the absorbent may be, for example,particulate or fibrous, and is selected properly according to therecovery system used, and, for example, the absorbent may be particulatewhen used in fluidized bed or fixed bed, while fibrous when used infixed bed.

The components in the recovered solvents may be restricted by thesolvents used during printing as described above, but the componentratio may vary according to the characteristics of the recovery device.For example, in a recovery device containing activated carbon asabsorbent, polar alcohols for example are less easily recovered becauseof low absorption efficiency, and high boiling point substances are lesseasily desorbed depending on the temperature setting during desorption.

The solvents captured by the absorbent are desorbed, for example, byintroduction of an inert gas such as air or nitrogen or heated gas suchas steam and/or by treating it under reduced pressure, and thenliquefied and collected in a storage tank shown in each pattern ofFIG. 1. The solvents have water content generally increased duringabsorption/desorption process. In particular, direct distillation of thesolvents as it may give a mixture having unintended water content,because of azeotropic distillation of solvent components with water.

Thus, a step of removing water from the recovered solvents may beinstalled additionally. Water is preferably removed, for example, bymembrane separation by using a polymer film such as polyimide film, aceramic film, or a zeolite film, adsorption by using for example silicagel, separation by using the difference in specific density, ordistillation. The water removal process may not be needed, if it ispossible to prevent contamination of water by control of the operationcondition, e.g., the humidity during absorption and desorption.

When the solvents obtained by recovery of vaporized solvents containthree or more solvents, the method according to the present inventionincludes a step of separating the mixed solvents into one or more singlesolvents, that is, mono solvents or pure solvents, and/or one or moreazeotropic mixtures of two or more solvents by multi-stage distillation.The multi-stage distillation may be carried out by common distillationoperation. Specifically, it may be carried out by batchwise distillationor continuous distillation. Because it is difficult theoretically andalso practically in batchwise distillation to obtain stabilizeddistillates, as the condition in the distillation column changescontinuously, use of continuous distillation is preferable forindustrial purpose.

Distillation columns are classified roughly into plate columns andpacked columns, and examples of the former columns include perforatedplate column, bubble column (baffle cup column), and valve column, andexamples of the latter columns include those containing various packingmaterials. The perforated plate column is simple structurally, lower inproduction cost, and lower in pressure drop, but disadvantageouslybecomes less stable in operation when the flow rate of the vapor drops,because the condensed vapor drops out of the holes therein. The bubblecolumn, a traditionally frequently used column, is disadvantageouslyhigher in production cost and higher in vapor pressure drop, butadvantageously allows continued operation even when the flow rate of thegas and liquid fluctuates. The valve column, which is more complexstructurally than the perforated plate column, controls its valveoperation by itself according to the flow rate of the vapor and has nosuch disadvantage like that of the perforated plate column. The packedcolumn is a column filled with a packing material such as Raschig rings,wherein the components are distributed between the liquid flowing downalong the surface of the packing material and the vapor flowing upwardthrough the opening that are in contact with each other. Thedistillation column is selected properly according to the desiredprocessing capacity and cost, and columns may be used in combination.

The performance of a distillation column is generally expressed with itstheoretical plate number, and the plate number is desirably higher forhigher separation efficiency. The theoretical plate number can becontrolled by the shape of the distillation column, the capacities ofreboiler and condenser, and the operational condition (heatingcondition, reflux ratio, distillation rate), and is selected properlyaccording to the desired processing capacity and cost and the desiredproperties of the recycled solvents such as purity.

Alternatively, the solvents may be separated as needed by extractiondistillation or azeotropic distillation by adding one or more othersolvents to the recovered solvent additionally. The extractiondistillation is a distillation method of separating a particularcomponent by adding a nonvolatile (high-boiling-point) liquid and thusshifting the equilibrium, and, for example, rectification of anazeotropic mixture of nitric acid and water in the presence of conc.nitric acid added gives conc. nitric acid from the column top. Theazeotropic distillation is a distillation method of separating anazeotropic mixture by addition of a volatile liquid, and, for example,rectification of an azeotropic mixture of ethanol and water in thepresence of added benzene gives an three-component azeotropic mixture ofethanol, water and benzene. Use of this method allows separation andrecycling of desired one or more single solvents and/or desired one ormore mixtures of solvents.

The method according to the present invention includes a step of reusingthe recovered solvents as printing ink raw materials and/or dilutionsolvent raw materials. The solvents according to the present inventionseparated by distillation of the recovered solvents are obtained in astabilized composition, and can be recycled as a raw material duringproduction of printing ink raw material and also as a raw material fordilution solvent.

The solvent-recoverable and recyclable printing ink compositionaccording to the present invention contains colorants, resins, andsolvents, and may contain as needed various additives. Thesolvent-recoverable and recyclable printing ink is coated on a basematerial by a printing process such as gravure printing or flexographicprinting; the solvents contained in the solvent-recoverable andrecyclable printing ink composition are vaporized in a dryer such asoven; and the vaporized solvents are recovered in a recovery devicecontaining an absorbent such as activated carbon. The solvents recoveredmay have a composition different from that of the original ink, becauseof the difference in adsorption efficiency among components, but in therecovered solvent-recycling method according to the present invention,the recovered solvents are obtained by distillation and fractionatedinto one or more single solvents and/or one or more azeotropiccompositions of two or more solvents by multi-stage distillation, andthe distillates are used for recycling after separation.

Examples of the multi-stage distillation of azeotropic solventcomposition include the followings (i) to (vi):

(i) In the case of a system of methylcyclohexane, methylethylketone,n-propyl acetate, isopropyl alcohol and propylene glycolmonomethylether, a mixed solvent having a component ratio of isopropylalcohol:methylethylketone:methylcyclohexane at 25 to 40 wt %:25 to 40 wt%:25 to 40 wt % is distilled at a column top temperature of around 74°C.;

(ii) In the case of a system of methylethylketone, n-propyl acetate,isopropyl alcohol, and propylene glycol monomethylether, a mixed solventhaving a component ratio of isopropyl alcohol:methylethylketone at 25 to45 wt %:55 to 75 wt % is distilled at a column top temperature of around75.5° C.;

(iii) In the case of a system of n-propyl acetate, isopropyl alcohol andpropylene glycol monomethylether, a mixed solvent having a componentratio of isopropyl alcohol:n-propyl acetate at 80 to 95 wt %:5 to 20 wt% is distilled at a column top temperature of around 76° C.;

(iv) In the case of a system of methylethylketone, n-propyl acetate andpropylene glycol monomethylether, methylethylketone solvent is distilledat a column top temperature of around 80° C.;

(v) In the case of a system of n-propyl acetate and propylene glycolmonomethylether, n-propyl acetate solvent is distilled and recovered ata column top temperature of around 102° C.; and

(vi) If propylene glycol monomethylether is contained in the system,propylene glycol monomethylether remains in the distillation still andrecovered from it.

The composition of the azeotropic mixture varies according to thecondition of the multi-stage distillation. If the composition of theazeotropic mixture is unknown, the method according to the presentinvention may include a step of analyzing the composition. Theanalytical method will be described below. If the composition isdetermined by compositional analysis and if separation of recoveredsolvents at a stabilized composition is possible, the mixed solvent inthe same composition can be recycled as a raw material for printing inkcomposition and dilution solvents, without intensive compositionalanalysis in the following and later operations.

For example, when a mixed solvent containing methylethylketone, n-propylacetate, and isopropyl alcohol at any ratio is desirably obtained, themixed solvent obtained in (ii) may be mixed with the methylethyl ketoneand n-propyl acetate obtained in (iv) and (V).

The analytical method is preferably a simple and easy, but accuratemeasurement method. Examples of the methods include gas chromatography,liquid chromatography, infrared absorption spectrometry, refractiveindex measurement, density measurement, conductivity measurement, andodor measurement.

In gas chromatography, a composition can be determined by measuring arecovered solvent sample and identifying the materials from theretention times and determining the amount thereof from the area ratios.The detector may be selected, for example, from TCD (thermalconductivity detector), FID (hydrogen flame ionization detector),according to desired accuracy. It is preferable that a calibration curveis formed before measurement and an internal standard substance is used.

Liquid chromatography is also carried out similarly to the gaschromatography by measuring a recovered solvent sample and determiningthe composition based on the area ratios on the chart obtained.

The infrared absorption spectrometry may be performed by a method ofplacing a sample in an isolated cell or a method of using a flow cellinstalled in the piping of the recovered solvents. The composition canbe calculated, based on the area ratios and light permeability (heights)of particular absorption band on the chart obtained. In the case of thismethod, absorption bands specific to the characteristic bonds of thesolvents should be identified previously, and, for example, the arearatio of the absorptions corresponding to ester bond C—O stretchingvibration and hydroxyl group O—H stretching vibration are determinedfrom the chart and the composition is determined. It is preferable thata calibration curve is formed before measurement and an internalstandard substance is used.

The refractive index measurement is a method of using the fact that asolvent has a refractive index specific to its chemical structure.Generally, D ray (Na flame, wavelength: 589 nm) is used as the lightsource for measurement, but a method of using sunlight or a method ofmeasuring absorbance by using light sources emitting lights different inwavelength and calculating the composition from the specific dispersionmay be used instead. It is preferable that a calibration curve is formedbefore measurement.

The density measurement can be used for analysis of components, becauseeach solvent component has a particular value. Examples of the measuringmethods include buoy method, hydrostatic balance method, and picnometricmethod, and the result is expressed by a numerical value such asspecific density, AIP degree, or Baume degree. It is preferable that acalibration curve is formed before measurement.

The conductivity measurement is a method using the fact that a solventhas a characteristic conductivity due to its chemical structure. Inparticular, an aqueous system may be used favorably, because water hashigh conductivity. It is preferable that a calibration curve is formedbefore measurement.

The nuclear magnetic resonance absorption method gives various patternsdue to the chemical structure of the analyte. Even the same C—H bondgives a signal different in chemical shift when it is present indifferent environment, and thus, a structurally characteristic bond ofsolvent is first identified, and it is possible to determine the amountof the solvent quantitatively by using the signal strength thereof at aparticular chemical shift. Generally, proton NMR or C¹³NMR, for example,is favorably used in identifying the organic compound by the nuclearmagnetic resonance absorption method. It is preferable that acalibration curve is formed before measurement.

The odor measurement may be performed organoleptically, for example, byusing odor index, but use of a device such as semiconductor gas sensoris more preferable for more rapid and accurate determination of thecomposition. The vapor quantity has a correlation with the blendingratio under the Raoult's law. It is preferable that a calibration curveis formed before measurement.

When the solvents obtained after recovery of vaporized solvents includetwo kinds of solvents, one component or a new component may be added tothe composition, after analysis of the solvent composition, to give adiluted solvent composition.

The dilute solvent-recoverable and recyclable solvents obtained by themethod may be used as an ink composition, a coating material, or alaminate coating material.

EXAMPLES

Hereinafter, the present invention will be described in more detail withreference to specific examples, but it should be understood that thescope of the present invention is not restricted by the followingExamples.

In the following Examples 1 to 4, the method of recovering and recyclingsolvents will be described, by using five kinds of solvent-recoverableand recyclable printing ink compositions containing solvents differentin blending rate. In the Examples below, part means wt part and % meanswt %; and the component ratio of respective solvents was determined fromgas chromatographic areas according to a previously prepared calibrationcurve.

Example 1

Gravure printing was performed by using solvent-recoverable andrecyclable printing inks different in resin composition that aredissolved in a solvent composition of isopropylalcohol/methylethylketone/methylcyclohexane/n-propyl acetate/propyleneglycol monomethylether in printing machines, and the solvents wererecovered collectively in a recovery device containing activated carbonparticles as in fluidized bed and dehydrated by a zeolite separationfilm, to give a recovered solvent composition (A) in the composition ofisopropyl alcohol:methylethylketone:methylcyclohexane:n-propylacetate:propylene glycol monomethylether at a ratio of25.0:15.0:5.0:50.0:5.0.

100 g of the recovered solvent composition (A) was placed in anErlenmeyer flask; a distillation column packed with Raschig rings wasconnected thereto; and the solvent composition was heated while stirredwith a hot stirrer.

Distillation of the recovered solvent composition at a reflux ratioequivalent to a reflux (Erlenmeyer flask):discharge (recovered solventcomposition) rate of 3:1 gave 16.0 g of a mixed solvent (a) of isopropylalcohol:methylethylketone:methylcyclohexane at a rate of 31.3:37.0:31.7(by weight) at a column top temperature of 74° C., 13.9 g of a mixedsolvent (b) of isopropyl alcohol:methylethylketone at a rate of34.3:65.7 (by weight) at a column top temperature of 75.5° C., then 16.9g of a mixed solvent (c) of isopropyl alcohol:n-propyl acetate at a rateof 89.2:10.8 (by weight) at a column top temperature of 80.5° C., and48.2 g of n-propyl acetate solvent (d) at a column top temperature of101° C.

The composionally-defined azeotropic mixed solvents (a) to (c), thesingle solvent (d), the single solvent of propylene glycolmonomethylether remaining in the Erlenmeyer flask (e) thus obtained wererecycled as raw materials for a printing ink composition and dilutionsolvents.

Example 2

A mixed solvent composition (B) was prepared by adding 40 parts ofmethylethylketone (X) to 100 parts of the recovered solvent composition(A) in Example 1.

100 g of the mixed solvent composition (B) was placed in an Erlenmeyerflask; a distillation column packed with Raschig rings was connectedthereto; and the solvent composition was heated while stirred with a hotstirrer.

Distillation of the recovered solvent composition at a reflux ratioequivalent to a reflux (Erlenmeyer flask):discharge (recovered solventcomposition) rate of 3:1 gave 16.0 g of a mixed solvent (a) of isopropylalcohol:methylethylketone:methylcyclohexane at a rate of 31.3:37.0:31.7(by weight) at a column top temperature of 74° C., then, 58.0 g of amixed solvent (b) of isopropyl alcohol:methylethylketone at a rate of34.3:65.7 (by weight) at a column top temperature of 75.5° C.,additionally methylethylketone solvent (f) at a column top temperatureof 78° C., and 48.2 g of n-propyl acetate solvent (d) at a column toptemperature of 101° C.

The composionally-defined azeotropic mixed solvents (a) and (b), thesingle solvents (d) and (f), and the propyleneglycol monomethylethermixed solvent remaining in the Erlenmeyer flask (e) thus obtained wererecycled as raw materials for the printing ink composition and dilutionsolvents. The methylethylketone solvent (f) was recycled in the nextdistillation also as (X).

Example 3

Gravure printing was performed by using solvent-recoverable andrecyclable printing inks different in resin composition that aredissolved in a mixed solvent composition of isopropylalcohol/methylethylketone/methylcyclohexane/n-propyl acetate/propyleneglycol monomethylether in more than one printing machines, and thesolvents were recovered collectively in a recovery device containingactivated carbon particles as in fluidized bed and dehydrated by azeolite separation film, to give a recovered solvent composition (A) inthe composition of isopropylalcohol:methylethylketone:methylcyclohexane:n-propyl acetate:propyleneglycol monomethylether at a ratio of 25.0:15.0:5.0:50.0:5.0 (by weight).100 g of the recovered solvent composition (A) was placed in anErlenmeyer flask; a distillation column packed with Raschig rings wasconnected thereto; and the solvent composition was heated while stirredwith a hot stirrer.

Distillation of the recovered solvent composition at a reflux ratioequivalent to a reflux (Erlenmeyer flask):discharge (recovered solventcomposition) rate of 3:1 gave 16.0 g of a mixed solvent (a) of isopropylalcohol:methylethylketone:methylcyclohexane at a rate of 31.3:37.0:31.7(by weight) at a column top temperature 74° C., 13.9 g of a mixedsolvent (b) of isopropyl alcohol:methylethylketone at a rate of34.3:65.7 (by weight) then at a column top temperature of 75.5° C., 16.9g of a mixed solvent (c) of isopropyl alcohol:n-propyl acetate at a rateof 89.2:10.8 (by weight) at a column top temperature of 80.5° C., and48.2 g of n-propyl acetate solvent (d) at a column top temperature of101° C.

The composionally-defined azeotropic mixed solvents (a) to (c), thesingle solvent (d), and 4.2 g of propylene glycol monomethylethersolvent remaining in the Erlenmeyer flask (e) thus obtained wererecycled as raw materials for the printing ink composition and dilutionsolvents.

Specifically, 100 parts of the recovered mixed solvent (c) and 256.8parts of the recovered mixed solvent (d) obtained in Example 3 weremixed, to give the n-propyl acetate/isopropanol mixed solvent (weightratio: 75/25) described below in Example 10, which was used as the rawmaterial for inks (B1) and (B3). Other mixed solvents were also recycledas they were blended with other mixed solvent or an unused solvent.

Example 4

A mixed solvent composition (B) was prepared by adding 40 parts ofmethylethylketone (X) to 100 parts of the recovered solvent composition(A) in Example 1. 140 g of the mixed solvent composition (B) was placedin an Erlenmeyer flask; a distillation column packed with Raschig ringswas connected thereto; and the solvent composition was heated whilestirred with a hot stirrer.

Distillation of the recovered solvent composition at a reflux ratioequivalent to a reflux (Erlenmeyer flask):discharge (recovered solventcomposition) rate of 3:1 gave 16.0 g of a mixed solvent (a) of isopropylalcohol:methylethylketone:methylcyclohexane at a rate of 31.3:37.0:31.7(by weight) at a column top temperature of 74° C., then, 58.0 g of amixed solvent (b) of isopropyl alcohol:methylethylketone at a rate of34.3:65.7 (by weight) at a column top temperature of 75.5° C.,additionally, 10 g of methylethylketone solvent (f) at a column toptemperature of 78° C., and 48.2 g of n-propyl acetate solvent (d) at acolumn top temperature of 101° C.

The composionally-defined azeotropic mixed solvents (a) and (b), thesingle solvents (d) and (f), and 4.3 g of the mixed propylene glycolmonomethylether solvent remaining in the Erlenmeyer flask (e) thusobtained were recycled as raw materials for the printing ink compositionand dilution solvents.

The methylethylketone solvent (f) was recycled in the next distillationalso as (X).

Hereinafter in the following Examples 5 to 8, the recovered solvent fromthe solvent-recoverable and recyclable printing ink containing two kindsof solvents will be analyzed by various analytical methods, and themethod of recycling the solvents will be described.

Example 5

Gravure printing was performed by using a solvent-recoverable andrecyclable printing ink containing nonvolatile solvents in thecomposition of ethyl acetate/isopropyl alcohol at a rate of 65/35, andthe vaporized solvent components were recovered in a recovery devicecontaining activated carbon particles as in fluidized bed and dehydratedby a zeolite separation film, to give a recovered mixed solvent (A) ofethyl acetate/isopropyl alcohol. 5 μl of the recovered solvent (A) wasanalyzed in a gas chromatograph “GC-8A” manufactured by ShimadzuCorporation equipped with a TCD detector and a glass column, showing achromatogram peak area ratio of ethylacetate/isopropyl alcohol at189105:92196. The component ratio of ethyl acetate/isopropyl alcohol inthe recovered solvent (A) was calculated to be 70/30 from a calibrationcurve previously prepared, and thus, isopropyl alcohol was added to therecovered solvent (A) to an ethyl acetate/isopropyl alcohol ratio of65/35, and the mixture was recycled as the raw material for the printingink.

Example 6

1 g of butanol was added to 10 g of the recovered solvent (A) obtainedin Example 5 as internal standard, to give a sample (B); 150 μl of thesample (B) was analyzed with a liquid chromatograph equipped with arefractive index detector “RI-101” manufactured by Shoko Co., Ltd. andfour liquid chromatography columns “LF-804” manufactured by Shoko Co.,Ltd., to show the peaks derived from ethylacetate, isopropylalcohol, andbutanol. The ratio of ethyl acetate/isopropyl alcohol in sample (B), ascalculated from calibration curves previously formed for ethyl acetateand isopropyl alcohol, was 70/30. Thus, isopropyl alcohol was added tothe recovered solvent (A), to an ethyl acetate/isopropyl alcohol ratioof 65/35, and the mixture was recycled as the raw material for theprinting ink.

Example 7

An FT-IR spectrum of the recovered solvent (A) obtained in Example 5 wasobtained by measurement by using an infrared spectrophotometer“JIR-WINSPEC 50” manufactured by JEOL. The absorption band at 1735 cm⁻¹,which was assigned to C═O stretching vibration of the ester bond inethyl acetate, and the broad absorption band at approximately 3450 cm⁻¹,which was assigned to O—H stretching vibration of the hydroxyl group inisopropyl alcohol, were determined, and the transmission ratio thereofwas 40.53/32.14. The ratio of ethylacetate to isopropylalcohol in therecovered solvent (A), ethyl acetate/isopropyl alcohol, as determinedbased on a previously prepared calibration curve, was 70/30. Thus,isopropyl alcohol was added to the recovered solvent (A) to an ethylacetate/isopropyl alcohol ratio of 65/35, and the mixture was recycledas the raw material for the printing ink.

Example 8

The specific density of the recovered solvent (A) obtained in Example 5,as determined in a 100-ml weighing bottle, was 8.412 (25° C.). The ratioof ethyl acetate to isopropyl alcohol in the recovered solvent (A),ethyl acetate/isopropyl alcohol as determined based on a calibrationcurve previously prepared, was 70/30. Thus, isopropyl alcohol was addedto the recovered solvent (A) to an ethyl acetate/isopropyl alcohol ratioof 65/35, and the mixture was recycled as the raw material for theprinting ink.

Hereinafter in Examples 9 to 23, ink compositions containing two orthree kinds of solvents were prepared, and the superiority thereof inprintability to the ink compositions of Comparative Examples 1 and 2will be described. In the following Examples and Comparative Examples,part and % mean wt parts and wt %, respectively. The amount of hydroxylgroup is determined in conformity with JIS K0070 in terms of the amountof potassium hydroxide (mg) required to neutralize the hydroxyl groupsin 1 g of a resin. The amine value is the amount of potassium hydroxide(mg) equivalent to that of hydrochloric acid needed to neutralize theamino groups in 1 g of resin. The amine value was determined by themethod described below. The molecular weight and the molecular weightdistribution as polystyrene were determined by GPC (gel-permeationchromatography) in terms of molecular weight of polystyrene. The aminevalue was determined in the following manner:

[Determination of Amine Value]

0.5 to 2 g of a sample is weighed accurately (sample quantity: S g). 30ml of neutral ethanol (BDG neutral) was added to the weighed sample forsolubilization. The solution obtained was titrated with 0.2 mol/literethanolic hydrochloric acid solution (titer: f). At the end point, thesolution turns from green to yellow in color, the titer then is A ml.The amine value was calculated according to the following Formula(Formula 1):

Amine value=(A×f×0.2×56.108)/S  (Formula 1)

Example 9

54.719 parts of a polyester diol having a number-average molecularweight of 2000 obtained from adipic acid and 2-butyl-2-ethylpropanediol,3.989 parts of isophorone diisocyanate, 0.010 part of stannous2-ethylhexanoate and 10.0 parts of n-propyl acetate were allowed toreact under nitrogen stream at 85° C. for 3 hours; 10.0 parts ofn-propyl acetate was added thereto; and the mixture was cooled, to give78.718 parts of a solvent solution of a terminal isocyanate prepolymer.Then, 78.718 parts of the solvent solution of a terminal isocyanateprepolymer obtained was gradually added to a mixture of 1.031 parts ofisophoronediamine, 0.261 part of di-n-butylamine, 30.4 parts of n-propylacetate and 19.6 parts of isopropyl alcohol at room temperature; themixture was then allowed to react at 50° C. for 1 hour, to give apolyurethane resin solution (A) having a solid content of 30% andcontaining a polymer having a weight-average molecular weight of 60,000and an amine value of 3.0 mg-KOH/g-resin.

30 parts of Titanix JR-805 (manufactured by Tayca Corporation), 10 partsof polyurethane resin solution (A), and 10.0 parts of an n-propylacetate/isopropyl alcohol mixture solution (weight ratio: 72/28) weremixed under agitation and kneaded in a sand mill; and 40 parts of thepolyurethane resin solution (A) and 10.0 parts of an n-propylacetate/isopropyl alcohol mixture solution (weight ratio: 72/28) weremixed with it, to give a white printing ink (A1). 50 parts of ann-propyl acetate/isopropyl alcohol mixture solution (weight ratio:72/28) was added as dilution solvent to 100 parts of the white printingink (A1) and was mixed, to give a white diluted ink (A2).

12 parts of copper phthalocyanine blue, 20 parts of the polyurethaneresin solution (A) and 10 parts of an n-propyl acetate/isopropyl alcoholmixture solution (weight ratio: 72/28) were mixed under agitation andkneaded in a sand mill; and 20 parts of the polyurethane resin solution(A) and 38 parts of an n-propyl acetate/isopropyl alcohol mixturesolution (weight ratio: 72/28) was added thereto, to give a blueprinting ink (A3). 50 parts of an n-propyl acetate/isopropyl alcoholmixture solution (weight ratio: 72/28) was added as dilution solvent to100 parts of the blue printing ink (A3) obtained and was mixed, to givea blue diluted ink (A4). The solvent composition of each of the dilutedinks thus obtained was n-propyl acetate/isopropyl alcohol at 72:28.

Example 10

78.718 parts of a solvent solution of a terminal isocyanate prepolymerwas prepared similarly to Example 9. Then, 78.718 parts of the solventsolution of a terminal isocyanate prepolymer obtained was graduallyadded to a mixture of 1.031 parts of isophoronediamine, 0.261 part ofdi-n-butylamine, 32.5 parts of n-propyl acetate and 17.5 parts ofisopropyl alcohol at room temperature; and the mixture was allowed toreact at 50° C. for 1 hour, to give a polyurethane resin solution (B)having a solid content of 30% and containing a polymer having aweight-average molecular weight of 60,000 and an amine value of 3.0mg-KOH/g-resin.

30 parts of Titanix JR-805 (manufactured by Tayca Corporation), 10 partsof the polyurethane resin solution (B), and 10.0 parts of an n-propylacetate/isopropyl alcohol mixture solution (weight ratio: 75/25) weremixed under agitation and kneaded in a sand mill; and 40 parts of thepolyurethane resin solution (B) and 10.0 parts of an n-propylacetate/isopropyl alcohol mixture solution (weight ratio: 75/25) weremixed with it, to give a white printing ink (B1). 50 parts of ann-propyl acetate/isopropyl alcohol mixture solution (weight ratio:75/25) was added as dilution solvent to the 100 parts of the whiteprinting ink (B1) obtained and was mixed, to give a white diluted ink(B2).

12 parts of copper phthalocyanine blue, 20 parts of the polyurethaneresin solution (B), and 10 parts of an n-propyl acetate/isopropylalcohol mixture solution (weight ratio: 75/25) were mixed underagitation and kneaded in a sand mill; and 20 parts of the polyurethaneresin solution (B) and 38 parts of an n-propyl acetate/isopropyl alcoholmixture solution (weight ratio: 75/25) were mixed with it, to give ablue printing ink (B3). 50 parts of an n-propyl acetate/isopropylalcohol mixture solution (weight ratio: 75/25) was added as dilutionsolvent to 100 parts of the blue printing ink (B3) obtained and wasmixed, to give a blue diluted ink (B4).

The solvent composition of each of the diluted inks thus obtained wasn-propyl acetate/isopropyl alcohol at 75:25.

Example 11

78.718 parts of a solvent solution of a terminal isocyanate prepolymerwas prepared similarly to Example 9. Then, 78.718 parts of the solventsolution containing a terminal isocyanate prepolymer obtained wasgradually added to a mixture of 1.031 parts of isophoronediamine, 0.261part of di-n-butylamine, 38.1 part of n-propyl acetate and 11.9 parts ofisopropyl alcohol at room temperature; the mixture was then allowed toreact at 50° C. for 1 hour, to give a polyurethane resin solution (C)having a solid content of 30% and containing a polymer having aweight-average molecular weight of 60,000 and an amine value of 3.0mg-KOH/g-resin.

30 parts of Titanix JR-805 (manufactured by Tayca Corporation), 10 partsof the polyurethane resin solution (C), and 10.0 parts of an n-propylacetate/isopropyl alcohol mixture solution (weight ratio: 83/17) weremixed under agitation and kneaded in a sand mill; and 40 parts of thepolyurethane resin varnish and 10.0 parts of an n-propylacetate/isopropyl alcohol mixture solution (weight ratio: 83/17) wereadded thereto, to give a white printing ink (C1). 50 parts of ann-propyl acetate/isopropyl alcohol mixture solution (weight ratio:83/17) was added as dilution solvent to 100 parts of the white printingink (C1) obtained and was mixed, to give a white diluted ink (C2).

12 parts of copper phthalocyanine blue, 20 parts of the polyurethaneresin solution (C), and 10 parts of an n-propyl acetate/isopropylalcohol mixture solution (weight ratio: 83/17) were mixed underagitation and kneaded in a sand mill; and 20 parts of the polyurethaneresin solution (C) and 38 parts of an n-propyl acetate/isopropyl alcoholmixture solution (weight ratio: 83/17) were mixed with it, to give ablue printing ink (C3). 50 parts of an n-propyl acetate/isopropylalcohol mixture solution (weight ratio: 83/17) was added as dilutionsolvent to 100 parts of the blue printing ink (C3) obtained and wasmixed, to give a blue diluted ink (C4). The solvent composition of eachof the diluted inks thus obtained was n-propyl acetate/isopropyl alcoholat 83:17.

Example 12

78.718 parts of a solvent solution of a terminal isocyanate prepolymerwas prepared similarly to Example 9. Then, 78.718 parts of the solventsolution of a terminal isocyanate prepolymer obtained was graduallyadded to a mixture of 1.031 parts of isophoronediamine, 0.261 part ofdi-n-butylamine, 23.1 parts of n-propyl acetate and 33.6 parts ofisopropyl alcohol at room temperature gradually; and the mixture wasthen allowed to react at 50° C. for 1 hour, to give a polyurethane resinsolution (D) having a solid content of 30% and containing a polymerhaving a weight-average molecular weight of 60,000 and an amine value of3.0 mg-KOH/g-resin.

30 parts of Titanix JR-805 (manufactured by Tayca Corporation), 10 partsof the polyurethane resin solution (D), and 10.0 parts of an n-propylacetate/isopropyl alcohol mixture solution (weight ratio: 52/48) weremixed under agitation and kneaded in a sand mill; and 40 parts of thepolyurethane resin solution (D) and 10.0 parts of an n-propylacetate/isopropyl alcohol mixture solution (weight ratio: 52/48) weremixed with it, to give a white printing ink (D1). 50 parts of ann-propyl acetate/isopropyl alcohol mixture solution (weight ratio:52/48) was added as dilution solvent to 100 parts of the white printingink (D1) obtained and was mixed, to give a white diluted ink (D2).

12 parts of copper phthalocyanine blue, 20 parts of the polyurethaneresin solution (D), and 10 parts of an n-propyl acetate/isopropylalcohol mixture solution (weight ratio: 52/48) were mixed underagitation and kneaded in a sand mill; and 20 parts of the polyurethaneresin solution (D) and 38 parts of an n-propyl acetate/isopropyl alcoholmixture solution (weight ratio: 52/48) were mixed with it, to give ablue printing ink (D3). 50 parts of an n-propyl acetate/isopropylalcohol mixture solution (weight ratio: 52/48) was added as dilutionsolvent to 100 parts of the blue printing ink (D3) obtained and wasmixed, to give a blue diluted ink (d4). The solvent composition of eachof the diluted inks thus obtained was n-propyl acetate/isopropyl alcoholat 52:48.

Example 13

78.718 parts of a solvent solution of a terminal isocyanate prepolymerwas prepared similarly to Example 9. Then, 78.718 parts of the solventsolution containing a terminal isocyanate prepolymer obtained wasgradually added to a mixture of 1.031 parts of isophoronediamine, 0.261part of di-n-butylamine, 22.6 parts of n-propyl acetate and 8.4 parts ofisopropyl alcohol at room temperature; and the mixture was allowed toreact at 50° C. for 1 hour, to give a polyurethane resin solution (E)having a solid content of 30% and containing a polymer having aweight-average molecular weight of 55,000 and an amine value of 3.0mg-KOH/g-resin.

30 parts of Titanix JR-805 (manufactured by Tayca Corporation), 10 partsof the polyurethane resin solution (E), and 10.0 parts of an n-propylacetate/isopropyl alcohol mixture solution (weight ratio: 88/12) weremixed under agitation and kneaded in a sand mill; and 40 parts of thepolyurethane resin solution (E) and 10.0 parts of an n-propylacetate/isopropyl alcohol mixture solution (weight ratio: 88/12) weremixed with it, to give a white printing ink (E1). 50 parts of ann-propyl acetate/isopropyl alcohol mixture solution (weight ratio:88/12) was added as dilution solvent to 100 parts of the white printingink (E1) obtained and was mixed, to give a white diluted ink (E2).

12 parts of copper phthalocyanine blue, 20 parts of the polyurethaneresin solution (E), and 10 parts of an n-propyl acetate/isopropylalcohol mixture solution (weight ratio: 88/12) were mixed underagitation and kneaded in a sand mill; and 20 parts of the polyurethaneresin solution (E) and 38 parts of an n-propyl acetate/isopropyl alcoholmixture solution (weight ratio: 88/12) were mixed with it, to give ablue printing ink (E3). 50 parts of an n-propyl acetate/isopropylalcohol mixture solution (weight ratio: 88/12) was added as dilutionsolvent to 100 parts of the blue printing ink (E3) obtained and wasmixed, to give a blue diluted ink (E4). The solvent composition of eachof the diluted inks thus obtained was n-propyl acetate/isopropyl alcoholat 88:12.

Example 14

78.718 parts of a solvent solution of a terminal isocyanate prepolymerwas prepared similarly to Example 9. Then, 78.718 parts of the solventsolution containing a terminal isocyanate prepolymer obtained wasgradually added to a mixture of 1.031 parts of isophoronediamine, 0.261part of di-n-butylamine, 8.0 parts of n-propyl acetate and 42.0 parts ofisopropyl alcohol at room temperature; and the mixture was then allowedto react at 50° C. for 1 hour, to give a polyurethane resin solution (F)having a solid content of 30% and containing a polymer having aweight-average molecular weight of 60,000 and an amine value of 3.0mg-KOH/g-resin.

30 parts of Titanix JR-805 (manufactured by Tayca Corporation), 10 partsof the polyurethane resin solution (F), and 10.0 parts of an n-propylacetate/isopropyl alcohol mixture solution (weight ratio: 40/60) weremixed under agitation and kneaded in a sand mill; and 40 parts of thepolyurethane resin solution (F) and 10.0 parts of an n-propylacetate/isopropyl alcohol mixture solution (weight ratio: 40/60) weremixed with it, to give a white printing ink (F1). 50 parts of ann-propyl acetate/isopropyl alcohol mixture solution (weight ratio:40/60) was added as dilution solvent to 100 parts of the white printingink (F1) obtained and was mixed, to give a white diluted ink (F2).

12 parts of copper phthalocyanine blue, 20 parts of the polyurethaneresin solution (F), and 10 parts of an n-propyl acetate/isopropylalcohol mixture solution (weight ratio: 40/60) were mixed underagitation and kneaded in a sand mill; and 20 parts of the polyurethaneresin solution (F) and 38 parts of an n-propyl acetate/isopropyl alcoholmixture solution (weight ratio: 40/60) were mixed with it, to give ablue printing ink (F3). 50 parts of an n-propyl acetate/isopropylalcohol mixture solution (weight ratio: 40/60) was added as dilutionsolvent to 100 parts of the blue printing ink (F3) obtained and wasmixed, to give a blue diluted ink (F4). The solvent composition of eachof the diluted inks thus obtained was n-propyl acetate/isopropyl alcoholat 40:60.

Example 15

78.718 parts of a solvent solution of a terminal isocyanate prepolymerwas prepared similarly to Example 9. Then, 78.718 parts of the solventsolution containing a terminal isocyanate prepolymer obtained wasgradually added to a mixture of 1.031 parts of isophoronediamine, 0.261part of di-n-butylamine, 46.5 parts of n-propyl acetate and 3.5 parts ofisopropyl alcohol at room temperature; and the mixture was allowed toreact at 50° C. for 1 hour, to give a polyurethane resin solution (G)having a solid content of 30% and containing a polymer having aweight-average molecular weight of 60,000 and an amine value of 3.0mg-KOH/g-resin.

30 parts of Titanix JR-805 (manufactured by Tayca Corporation), 10 partsof the polyurethane resin solution (G), and 10.0 parts of an n-propylacetate/isopropyl alcohol mixture solution (weight ratio: 95/5) weremixed under agitation and kneaded in a sand mill; and 40 parts of thepolyurethane resin solution (G) and 10.0 parts of an n-propylacetate/isopropyl alcohol mixture solution (weight ratio: 95/5) weremixed with it, to give a white printing ink (G1). 50 parts of ann-propyl acetate/isopropyl alcohol mixture solution (weight ratio: 95/5)was added as dilution solvent to 100 parts of the white printing ink(G1) obtained and was mixed, to give a white diluted ink (G2).

12 parts of copper phthalocyanine blue, 20 parts of the polyurethaneresin solution (G), and 10 parts of an n-propyl acetate/isopropylalcohol mixture solution (weight ratio: 95/5) were mixed under agitationand kneaded in a sand mill; and 20 parts of the polyurethane resinsolution (G) and 38 parts of an n-propyl acetate/isopropyl alcoholmixture solution (weight ratio: 95/5) were mixed with it, to give a blueprinting ink (G3). 50 parts of an n-propyl acetate/isopropyl alcoholmixture solution (weight ratio: 95/5) was added as dilution solvent to100 parts of the blue printing ink (G3) obtained and was mixed, to givea blue diluted ink (G4). The solvent composition of each of the dilutedinks thus obtained was n-propyl acetate/isopropyl alcohol at 95:5.

Example 16

54.719 parts of a polyester diol obtained from adipic acid and2-butyl-2-ethylpropanediol having a number-average molecular weight of2000, 3.989 parts of isophoronediisocyanate, 0.010 part of stannous2-ethylhexanoate and 10.0 parts of ethyl acetate were allowed to reactunder nitrogen stream at 85° C. for 3 hours; after addition of 10.0parts of ethyl acetate, the mixture was cooled, to give 78.718 parts ofa terminal isocyanate prepolymer solvent solution. Then, 78.718 parts ofthe terminal isocyanate prepolymer solvent solution obtained wasgradually added to a mixture of 1.031 parts of isophoronediamine, 0.261part of di-n-butylamine, 16.4 parts of ethyl acetate and 33.6 parts ofisopropyl alcohol at room temperature; and the mixture was allowed toreact at 50° C. for 1 hour, to give a polyurethane resin solution (H)having a solid content of 30% and containing a polymer having aweight-average molecular weight of 60,000 and an amine value of 3.0mg-KOH/g-resin.

30 parts of Titanix JR-805 (manufactured by Tayca Corporation), 10 partsof the polyurethane resin solution (H), and 10.0 parts of an ethylacetate/isopropyl alcohol mixture solution (weight ratio: 52/48) weremixed under agitation and kneaded in a sand mill; and 40 parts of thepolyurethane resin solution and 10.0 parts of an ethyl acetate/isopropylalcohol mixture solution (weight ratio: 52/48) were mixed with it, togive a white printing ink (H1). 50 parts of an ethyl acetate/isopropylalcohol mixture solution (weight ratio: 52/48) was added as dilutionsolvent to 100 parts of the white printing ink (H1) obtained and wasmixed, to give a white diluted ink (H2).

12 parts of copper phthalocyanine blue, 20 parts of the polyurethaneresin solution (H), and 10 parts of an ethyl acetate/isopropyl alcoholmixture solution (weight ratio: 52/48) were mixed under agitation andkneaded in a sand mill; and 20 parts of the polyurethane resin solution(H) and 38 parts of an ethyl acetate/isopropyl alcohol mixture solution(weight ratio: 52/48) were mixed with it, to give a blue printing ink(H3). 50 parts of an ethyl acetate/isopropyl alcohol mixture solution(weight ratio: 52/48) was added as dilution solvent to 100 parts of theblue printing ink (H3) obtained and was mixed, to give a blue dilutedink (H4). The solvent composition of each of the diluted inks thusobtained was ethyl acetate/isopropyl alcohol at 52:48.

Example 17

78.718 parts of a terminal isocyanate prepolymer solvent solution wasobtained similarly to Example 16. Then, 78.718 parts of the terminalisocyanate prepolymer solvent solution obtained was gradually added to amixture of 1.031 parts of isophoronediamine, 0.261 part ofdi-n-butylamine, 8.0 parts of ethyl acetate and 42.0 parts of isopropylalcohol at room temperature; and the mixture was allowed then to reactat 50° C. for 1 hour, to give a polyurethane resin solution (I) having asolid content of 30% and containing a polymer having a weight-averagemolecular weight of 60,000 and an amine value of 3.0 mg-KOH/g-resin.

30 parts of Titanix JR-805 (manufactured by Tayca Corporation), 10 partsof the polyurethane resin solution (I) and 10.0 parts of an ethylacetate/isopropyl alcohol mixture solution (weight ratio: 40/60) weremixed under agitation and kneaded in a sand mill; and 40 parts of thepolyurethane resin solution (I) and 10.0 parts of an ethylacetate/isopropyl alcohol mixture solution (weight ratio: 40/60) weremixed with it, to give a white printing ink (I1). 50 parts of an ethylacetate/isopropyl alcohol mixture solution (weight ratio: 40/60) wasadded as dilution solvent to 100 parts of the white printing ink (I1)obtained and was mixed, to give a white diluted ink (I2).

12 parts of copper phthalocyanine blue, 20 parts of the polyurethaneresin solution (I), and 10 parts of an ethyl acetate/isopropyl alcoholmixture solution (weight ratio: 40/60) were mixed under agitation andkneaded in a sand mill; and 20 parts of the polyurethane resin solution(I) and 38 parts of an ethyl acetate/isopropyl alcohol mixture solution(weight ratio: 40/60) were mixed with it, to give a blue printing ink(I3). 50 parts of an ethyl acetate/isopropyl alcohol mixture solution(weight ratio: 40/60) was added as dilution solvent to 100 parts of theblue printing ink (I3) obtained and was mixed, to give a blue dilutedink (I4).

The solvent composition of each of the diluted inks thus obtained wasethyl acetate/isopropyl alcohol at 40:60.

Example 18

78.718 parts of a terminal isocyanate prepolymer solvent solution wasobtained similarly to Example 16. Then, 78.718 parts of the terminalisocyanate prepolymer solvent solution obtained was gradually added to amixture of 1.031 parts of isophoronediamine, 0.261 part ofdi-n-butylamine, 5.4 parts of ethyl acetate and 54.6 parts of n-propylalcohol at room temperature; and the mixture was allowed to react at 50°C. for 1 hour, to give a polyurethane resin solution (J) having a solidcontent of 30% and containing a polymer having a weight-averagemolecular weight of 55,000, an amine value of 3.0 mg-KOH/g-resin, and aviscosity at 25° C. of 600 mPa·S.

30 parts of Titanix JR-805 (manufactured by Tayca Corporation), 10 partsof the polyurethane resin solution (J), and 10.0 parts of an ethylacetate/n-propyl alcohol mixture solution (weight ratio: 22/78) weremixed under agitation and kneaded in a sand mill; and 40 parts of thepolyurethane resin solution (J) and 10.0 parts of an ethylacetate/n-propyl alcohol mixture solution (weight ratio: 22/78) weremixed with it, to give a white printing ink (J1). 50 parts of an ethylacetate/n-propyl alcohol mixture solution (weight ratio: 22/78) wasadded as dilution solvent to 100 parts of the white printing ink (J1)obtained and was mixed, to give a white diluted ink (J2).

12 parts of copper phthalocyanine blue, 20 parts of the polyurethaneresin solution, and 10 parts of an ethyl acetate/n-propyl alcoholmixture solution (weight ratio: 22/78) were mixed under agitation andkneaded in a sand mill; and 20 parts of the polyurethane resin solution(J) and 38 parts of an ethyl acetate/n-propyl alcohol mixture solution(weight ratio: 22/78) were mixed with it, to give a blue printing ink(J3). 50 parts of an ethyl acetate/n-propyl alcohol mixture solution(weight ratio: 22/78) was added as dilution solvent to 100 parts of theblue printing ink (BJ) obtained and was mixed, to give a blue dilutedink (J4).

The solvent composition of each of the diluted inks thus obtained wasethyl acetate/n-propyl alcohol at 22:78.

Example 19

78.718 parts of a terminal isocyanate prepolymer solvent solution wasobtained similarly to Example 16. Then, 78.718 parts of the terminalisocyanate prepolymer solvent solution obtained was gradually added to amixture of 1.031 parts of isophoronediamine, 0.261 part ofdi-n-butylamine, 32.5 parts of ethyl acetate and 17.5 parts of isopropylalcohol at room temperature; and the mixture was allowed to react at 50°C. for 1 hour, to give a polyurethane resin solution (K) having a solidcontent of 30% and containing a polymer having a weight-averagemolecular weight of 60,000 and an amine value of 3.0 mg-KOH/g-resin.

30 parts of Titanix JR-805 (manufactured by Tayca Corporation), 10 partsof the polyurethane resin solution (K), and 10.0 parts of an ethylacetate/isopropyl alcohol mixture solution (weight ratio: 75/25) weremixed under agitation and kneaded in a sand mill; and 40 parts of thepolyurethane resin solution (K), and 10.0 parts of an ethylacetate/isopropyl alcohol mixture solution (weight ratio: 75/25) weremixed with it, to give a white printing ink (K1). 50 parts of an ethylacetate/isopropyl alcohol mixture solution (weight ratio: 75/25) wasadded as dilution solvent to 100 parts of the white printing ink (K1)obtained and was mixed, to give a white diluted ink (K2).

12 parts of copper phthalocyanine blue, 20 parts of the polyurethaneresin solution (K), and 10 parts of an ethyl acetate/isopropyl alcoholmixture solution (weight ratio: 75/25) were mixed under agitation andkneaded in a sand mill; and 20 parts of the polyurethane resin solution(K) and 38 parts of an ethyl acetate/isopropyl alcohol mixture solution(weight ratio: 75/25) were mixed with it, to give a blue printing ink(K3). 50 parts of an ethyl acetate/isopropyl alcohol mixture solution(weight ratio: 75/25) was added as dilution solvent to 100 parts of theblue printing ink (K3) obtained, to give a blue diluted ink (K4). Thesolvent composition of each of the diluted inks thus obtained was ethylacetate/isopropyl alcohol at 75:25.

Example 20

54.719 parts of a polyester diol obtained from adipic acid and2-butyl-2-ethylpropanediol having a number-average molecular weight of2000, 3.989 parts of isophoronediisocyanate, 0.010 part of stannous2-ethylhexanoate and 10.0 parts of isobutyl acetate were allowed toreact under nitrogen stream at 85° C. for 3 hours; 10.0 parts ofisobutyl acetate was added thereto, to give 78.718 parts of a terminalisocyanate prepolymer solvent solution. Then, 78.718 parts of theterminal isocyanate prepolymer solvent solution obtained was graduallyadded to a mixture of 1.031 parts of isophoronediamine, 0.261 part ofdi-n-butylamine, 32.5 parts of isobutyl acetate and 17.5 parts ofisopropyl alcohol at room temperature; and the mixture was allowed toreact at 50° C. for 1 hour, to give a polyurethane resin solution (L)having a solid content of 30% and containing a polymer having aweight-average molecular weight of 60,000 and an amine value of 3.0mg-KOH/g-resin.

30 parts of Titanix JR-805 (manufactured by Tayca Corporation), 10 partsof the polyurethane resin solution (L) and 10.0 parts of an isobutylacetate/isopropyl alcohol mixture solution (weight ratio: 75/25) weremixed under agitation and kneaded in a sand mill; and 40 parts of thepolyurethane resin solution (L) and 10.0 parts of an isobutylacetate/isopropyl alcohol mixture solution (weight ratio: 75/25) weremixed with it, to give a white printing ink (L1). 50 parts of anisobutyl acetate/isopropyl alcohol mixture solution (weight ratio:75/25) was added as dilution solvent to 100 parts of the white printingink (L1) obtained and was mixed, to give a white diluted ink (L2).

12 parts of copper phthalocyanine blue, 20 parts of the polyurethaneresin solution (L) and 10 parts of an isobutyl acetate/isopropyl alcoholmixture solution (weight ratio: 75/25) were mixed under agitation andkneaded in a sand mill; and 20 parts of the polyurethane resin solution(L) and 38 parts of an isobutyl acetate/isopropyl alcohol mixturesolution (weight ratio: 75/25) were mixed with it, to give a blueprinting ink (L3). 50 parts of an isobutyl acetate/isopropyl alcoholmixture solution (weight ratio: 75/25) was added as dilution solvent to100 parts of the blue printing ink (L3) obtained, to give a blue dilutedink (L4).

The solvent composition of each of the diluted inks thus obtained wasisobutyl acetate/isopropyl alcohol at 75:25.

Example 21

78.718 parts of a solvent solution of a terminal isocyanate prepolymerwas prepared similarly to Example 9. Then, 78.718 parts of the terminalisocyanate prepolymer solvent solution obtained was gradually added to amixture of 1.031 parts of isophoronediamine, 0.261 part ofdi-n-butylamine, 32.5 parts of n-propyl acetate and 17.5 parts ofn-propyl alcohol at room temperature; the mixture was allowed to reactat 50° C. for 1 hour, to give a polyurethane resin solution (M) having asolid content of 30% and containing a polymer having a weight-averagemolecular weight of 60,000 and an amine value of 3.0 mg-KOH/g-resin.

30 parts of Titanix JR-805 (manufactured by Tayca Corporation), 10 partsof the polyurethane resin solution (M) and 10.0 parts of an n-propylacetate/n-propyl alcohol mixture solution (weight ratio: 75/25) weremixed under agitation and kneaded in a sand mill; and 40 parts of thepolyurethane resin solution (M) and 10.0 parts of an n-propylacetate/n-propyl alcohol mixture solution (weight ratio: 75/25) weremixed with it, to give a white printing ink (M1). 50 parts of ann-propyl acetate/n-propyl alcohol mixture solution (weight ratio: 75/25)was added as dilution solvent to 100 parts of the white printing ink(M1) obtained and was mixed, to give a white diluted ink (M2).

12 parts of copper phthalocyanine blue, 20 parts of the polyurethaneresin solution (M) and 10 parts of an n-propyl acetate/n-propyl alcoholmixture solution (weight ratio: 75/25) were mixed under agitation andkneaded in a sand mill; and 20 parts of the polyurethane resin solution(M) and 38 parts of an n-propyl acetate/n-propyl alcohol mixturesolution (weight ratio: 75/25) were mixed with it, to give a blueprinting ink (M3). 50 parts of an n-propyl acetate/n-propyl alcoholmixture solution (weight ratio: 75/25) was added as dilution solvent to100 parts of the blue printing ink (M3) obtained, to give a blue dilutedink (M4). The solvent composition of each of the diluted inks thusobtained was n-propyl acetate/n-propyl alcohol at 75:25.

Example 22

78.718 parts of a solvent solution of a terminal isocyanate prepolymerwas prepared similarly to Example 9. Then, 78.718 parts of the terminalisocyanate prepolymer solvent solution obtained was gradually added to amixture of 1.031 parts of isophoronediamine, 0.261 part ofdi-n-butylamine, 32.5 parts of n-propyl acetate and 17.5 parts ofpropylene glycol monoethylether at room temperature; and the mixture wasallowed to react at 50° C. for 1 hour, to give a polyurethane resinsolution (N) having a solid content of 30% and containing a polymerhaving a weight-average molecular weight of 60,000, an amine value of3.0 mg-KOH/g-resin, and a viscosity at 25° C. of 600 mPa·S.

30 parts of Titanix JR-805 (manufactured by Tayca Corporation), 10 partsof the polyurethane resin solution (N) and 10.0 parts of an n-propylacetate/propylene glycol monoethylether mixture solution (weight ratio:75/25) were mixed under agitation and kneaded in a sand mill; and 40parts of the polyurethane resin solution (N) and 10.0 parts of ann-propyl acetate/propylene glycol monoethylether mixture solution(weight ratio: 75/25) were mixed with it, to give a white printing ink(N1). 50 parts of an n-propyl acetate/propylene glycol monoethylethermixture solution (weight ratio: 75/25) was added as dilution solvent to100 parts of the white printing ink (N1) obtained and was mixed, to givea white diluted ink (N2).

12 parts of copper phthalocyanine blue, 20 parts of the polyurethaneresin solution (N) and 10 parts of an n-propyl acetate/propylene glycolmonoethylether mixture solution (weight ratio: 75/25) were mixed underagitation and kneaded in a sand mill; and 20 parts of the polyurethaneresin solution (N) and 38 parts of an n-propyl acetate/propylene glycolmonoethylether mixture solution (weight ratio: 75/25) were mixed withit, to give a blue printing ink (N3). 50 parts of an n-propylacetate/propylene glycol monoethylether mixture solution (weight ratio:75/25) was added as dilution solvent to 100 parts of the blue printingink (N3) obtained and was mixed, to give a blue diluted ink (N4).

The solvent composition of each of the diluted inks thus obtained wasn-propyl acetate/propylene glycol monoethylether at 75:25.

Comparative Example 1

78.718 parts of a solvent solution of a terminal isocyanate prepolymerwas prepared similarly to Example 9. Then, 78.718 parts of the terminalisocyanate prepolymer solvent solution obtained was gradually added to amixture of 1.031 parts of isophoronediamine, 0.261 part ofdi-n-butylamine and 50.0 parts of n-propyl acetate at room temperature;and the mixture was allowed to react at 50° C. for 1 hour, to give apolyurethane resin solution (O) having a solid content of 30% andcontaining a polymer having a weight-average molecular weight of 20,000,an amine value of 3.0 mg-KOH/g-resin, and a viscosity at 25° C. of 600mPa·S.

30 parts of Titanix JR-805 (manufactured by Tayca Corporation), 10 partsof the polyurethane resin solution (O) and 10.0 parts of n-propylacetate were mixed under agitation and kneaded in a sand mill; and 40parts of the polyurethane resin solution (O) and 10.0 parts of n-propylacetate were mixed with it, to give a white printing ink (O1). 50 partsof n-propyl acetate was added as dilution solvent to 100 parts of thewhite printing ink obtained (O1) and was mixed, to give a white dilutedink (O2).

12 parts of copper phthalocyanine blue, 20 parts of the polyurethaneresin solution (O) and 10 parts of n-propyl acetate were mixed underagitation and kneaded in a sand mill; and 20 parts of polyurethane resinsolution (O) and 38 parts of n-propyl acetate were mixed with it, togive a blue printing ink (O3). 50 parts of n-propyl acetate was added asdilution solvent to 100 parts of the blue printing ink obtained (O3) andwas mixed, to give a blue diluted ink (O4).

Thus, the solvent for the diluted ink was n-propyl acetate.

Comparative Example 2

54.719 parts of a polyester diol obtained from adipic acid andbutylethylpropanediol and having a number-average molecular weight of2000, 3.989 parts of isophorone diisocyanate, 0.010 part of stannous2-ethylhexanoate and 10.0 parts of isopropyl alcohol were allowed toreact under nitrogen stream at 85° C. for 3 hours; and, after additionof 10.0 parts of isopropyl alcohol, the mixture was cooled, to give78.718 parts of a terminal isocyanate prepolymer solvent solution. Then,78.718 parts of the terminal isocyanate prepolymer solvent solutionobtained was gradually added to a mixture of 1.031 parts ofisophoronediamine, 0.261 part of di-n-butylamine and 50.0 parts ofisopropyl alcohol at room temperature; and the mixture was allowed toreact at 50° C. for 1 hour, to give a polyurethane resin solution (P)having a solid content of 30% and containing a polymer having aweight-average molecular weight of 20,000, an amine value of 3.0mg-KOH/g-resin, and a viscosity at 25° C. of 600 mPa·S.

30 parts of Titanix JR-805 (manufactured by Tayca Corporation), 10 partsof the polyurethane resin solution (P) and 10.0 parts of isopropylalcohol were mixed under agitation and kneaded in a sand mill; and 40parts of the polyurethane resin solution (P) and 10.0 parts of isopropylalcohol were mixed with it, to give a white printing ink (P1). 50 partsof isopropyl alcohol was added as dilution solvent to 100 parts of thewhite printing ink obtained (P1) and was mixed, to give a white dilutedink (P2).

12 parts of copper phthalocyanine blue, 20 parts of the polyurethaneresin solution (P) and 10 parts of isopropyl alcohol were mixed underagitation and kneaded in a sand mill; and 20 parts of the polyurethaneresin solution (P) and 38 parts of isopropyl alcohol were mixed with it,to give a blue printing ink (P3). 50 parts of isopropyl alcohol wasadded as dilution solvent to 100 parts of the blue printing ink obtained(P3) and was mixed, to give a blue diluted ink (P4). Thus, the solventfor the diluted ink was isopropyl alcohol.

Example 23

54.719 parts of a polyester diol obtained from adipic acid andbutylethylpropanediol and having a number-average molecular weight of2000, 3.989 parts of isophorone diisocyanate, 0.010 part of stannous2-ethylhexanoate and 10.0 parts of an ethyl acetate/n-propyl acetatemixture solution (weight ratio: 1/2) were allowed to react undernitrogen stream at 85° C. for 3 hours; after addition of 10.0 parts of aethyl acetate/n-propyl acetate mixture solution (weight ratio: 1/2), themixture was cooled, to give 78.718 parts of a terminal isocyanateprepolymer solvent solution. Then, 78.718 parts of the terminalisocyanate prepolymer solvent solution obtained was gradually added to amixture of 1.031 parts of isophoronediamine, 0.261 part ofdi-n-butylamine, 32.5 parts of an ethyl acetate/n-propyl acetate mixturesolution (weight ratio: 1/2) and 17.5 parts of isopropyl alcohol at roomtemperature; and the mixture was then allowed to react at 50° C. for 1hour, to give a polyurethane resin solution (Q) having a solid contentof 30% and containing a polymer having a weight-average molecular weightof 60,000, an amine value of 3.0 mg-KOH/g-resin, and a viscosity at 25°C. of 600 mPa·S.

30 parts of Titanix JR-805 (manufactured by Tayca Corporation), 10 partsof the polyurethane resin solution (Q) and 10.0 parts of an ethylacetate/n-propyl acetate/isopropyl alcohol mixture solution (weightratio: 25/50/25) were mixed under agitation and kneaded in a sand mill;and 40 parts of the polyurethane resin solution (Q) and 10.0 parts of anethyl acetate/n-propyl acetate/isopropyl alcohol mixture solution(weight ratio: 25/50/25) were mixed with it, to give a white printingink (Q1). 50 parts of an ethyl acetate/n-propyl acetate/isopropylalcohol mixture solution (weight ratio: 25/50/25) was added as dilutionsolvent to 100 parts of the white printing ink obtained (Q1) and wasmixed, to give a white diluted ink (Q2).

12 parts of copper phthalocyanine blue, 20 parts of the polyurethaneresin solution (Q0) and 10 parts of an ethyl acetate/n-propylacetate/isopropyl alcohol mixture solution (weight ratio: 25/50/25) weremixed under agitation and kneaded in a sand mill; and 20 parts of thepolyurethane resin solution (Q) and 38 parts of an ethylacetate/n-propyl acetate/isopropyl alcohol mixture solution (weightratio: 25/50/25) were mixed with it, to give a blue printing ink (Q3).50 parts of an n-propyl acetate/isopropyl alcohol mixture solution(weight ratio: 75/25) was added as dilution solvent to 100 parts of theblue printing ink obtained (Q3) and was mixed, to give a blue dilutedink (Q4). The solvent composition of each of the diluted inks thusobtained was ethyl acetate/n-propyl acetate/isopropyl alcohol at25:75:25.

Examples 9 to 23 and Comparative Examples 1 to 2

Properties of each of the diluted printing inks A4 to Q4 obtained inExamples 9 to 23 and Comparative Examples 1 to 2 were evaluated in thefollowing manner:

[Printability]

An impression drum of NBR (nitrile butadiene rubber) having a rubberhardness of 80 Hs, a ceramic-plated doctor blade having an edgethickness of 60 μm (base material thickness: 40 μm, one-sided ceramiclayer thickness: 10 μm), an electronically engraving plate having achromium hardness of 1050 Hv manufactured by Toyo Prepress Co., Ltd.(stylus angle: 120°, for color ink: 250 lines/inch, for white ink: 200lines/inch), and the diluted printing ink obtained in each of Examples 9to 23 and Comparative Examples 1 and 2 were placed in a gravure printingmachine manufactured by Fuji Kikai Kogyo Co. Ltd.; the plate waspreconditioned by rotation at a doctor-blade pressure of 2 kg/cm² and arotational velocity of 100 m/minute for 60 minutes; and then, the inkwas printed on the corona-finished surface of a one-face corona-treatedOPP film “Pylen P2161 (manufactured by Toyobo Co., Ltd.)” at a printingspeed of 100 m/minute and a pressure of 2 kg/cm² and then dried with hotair at 60° C., to give a print. During printing, the ink was adjusted toa particular viscosity by replenishment of each dilution solvent fed bya viscosity controller.

1. A stained print sample was bonded onto a black or white paper, andthe amount of the ink deposited on the margin region (unlined region) ofthe paper was visually evaluated according to the following criteria:

VG: No ink transfer observed in the nonimage region.

G: Slight ink transfer observed in the nonimage region.

F: Ink transfer observed in a small area of nonimage region.

P: Ink transfer observed in a large area of nonimage region.

VP: Ink transfer observed in the entire area of nonimage region.

2. Staining on impression drum after printing was evaluated visually.

VG: No ink transfer observed on the impression drum surface.

G: Slight ink transfer observed on the impression drum surface.

F: Ink transfer observed on a small area of the impression drum surface.

P: Ink transfer observed on a large area of the impression drum surface.

VP: Ink transfer observed on the entire surface of the impression drum.

3. The reactivity of the used solvents with an isocyanategroup-containing hardening agent commonly used as a hardening agent inisocyanate-reactive gravure inks was determined. When a solvent highlyreactive is used, the isocyanate groups react with the solvent duringprinting, resulting in loss of the ability to form a strong coated filmof the resin used by crosslinking.

VG: Solvent containing no hydroxyl group.

G: Solvent containing secondary hydroxyl groups.

F: Solvent containing primary hydroxyl groups.

P: Solvent containing one or more groups more reactive than hydroxylgroup, such as amino groups.

TABLE 1 Organic solvent component ratio Printability Alcohol White BluePropylene Urethane Impres- Impres- Iso- Ester glycol resin sion sioncyanate Ethyl n-Propyl Isobutyl n-Propyl Isopropyl monoethyl- solutionPrint drum Print drum reactiv- acetate acetate acetate alcohol alcoholether Mw staining staining staining staining ity Example 9 72 28 60000VG VG VG VG G 10 75 25 60000 VG VG VG VG G 11 83 17 60000 VG VG VG VG G12 52 48 60000 F VG G VG G 13 88 12 60000 G VG G VG G 14 40 60 55000 FVG F VG G 15 95 5 60000 F VG F VG G 16 52 48 60000 G VG VG VG G 17 40 6060000 G VG VG VG G 18 22 78 55000 G VG G VG G 19 75 25 60000 F VG F G G20 75 25 60000 VG F VG F G 21 75 25 40000 VG VG VG VG F 22 75 25 60000VG F VG G G 23 25 50 25 60000 VG VG VG VG G Compar- 1 100 Whitening — —— — VG ative (unsuc- Example cessful synthesis) 2 100 Whitening — — — —G (unsuc- cessful synthesis)

1-25. (canceled)
 26. A solvent-recoverable and recyclable printing inkcomposition, comprising solvents, wherein 95% or more of total amount ofthe solvents comprise two organic solvents, the two organic solvents aren-propyl acetate and isopropyl alcohol.
 27. The solvent-recoverable andrecyclable printing ink composition according to claim 26 wherein theweight ratio of n-propyl acetate to isopropyl alcohol is in the range of60:40 to 90:10.
 28. The solvent-recoverable and recyclable printing inkcomposition according to claim 27, wherein the weight ratio of n-propylacetate to isopropyl alcohol is in the range of 70:30 to 85:15.
 29. Thesolvent-recoverable and recyclable printing ink composition according toclaim 26, wherein the composition comprises a polyurethane resin formedfrom a polymer polyol, an organic isocyanate compound and a chainextender as a main binder.
 30. A solvent-recoverable and recyclabledilution solvent composition, characterized by being same kinds of theorganic solvents in the solvent-recoverable and recyclable printing inkcomposition according to claim
 26. 31. A coated article, comprising thesolvent-recoverable and recyclable printing ink composition according toclaim
 26. 32. A laminated article, prepared by a method comprising thesteps of coating the solvent-recoverable and recyclable printing inkcomposition according to claim 26 on a film, and laminating orcompression-bonding the film thus obtained.
 33. A method of recoveringand recycling solvents, which comprises: a step of recovering solventsvaporized in a solvent recovery apparatus during printing or coatingwith a solvent-recoverable and recyclable printing ink composition, anda step of recycling the solvents as a printing ink raw material or adilution solvent raw material, wherein the printing ink compositioncomprises solvents, 95% or more of total amount of the solvents comprisetwo organic solvents, and the two organic solvents are n-propyl acetateand isopropyl alcohol.
 34. The method of recovering and recyclingsolvents according to claim 33, which further comprises a step ofanalyzing the composition of the solvents after the step of recoveringbefore the step of recycling solvents.
 35. The method of recovering andrecycling solvents according to claim 33, wherein the step of analyzingsolvents comprises a step of adding n-propyl acetate or isopropylalcohol into the solvents to adjust weight ratio of solvents.
 36. Themethod of recovering and recycling solvents according to claim 33,wherein the weight ratio of n-propyl acetate to isopropyl alcohol is inthe range of 60:40 to 90:10.
 37. The method of recovering and recyclingsolvents according to claim 36, wherein weight ratio of n-propyl acetateto isopropyl alcohol is in the range of 70:30 to 85:15.
 38. The methodof recovering and recycling solvents according to claim 34, wherein thestep of analyzing solvents is carried out by at least one methodselected from gas chromatography, liquid chromatography, infraredabsorption spectrometry, refractive index measurement, density ratiomeasurement, conductivity measurement, nuclear magnetic resonanceabsorption method and odor test method.
 39. A printing ink composition,comprising the solvents obtained by the method according to claim 33.40. A printing ink dilution composition, comprising the solventsobtained by the method according to claim 33.